1. Field of the Invention
The invention relates to a blow-off device for a bypass gas turbine engine, such as a bypass turbojet turbine-engine.
2. Discussion of the Prior Art
It is known, for example from U.S. Pat. No. 3,638,428, to fit blow-off members in the wall of the primary air flow path between the low pressure compressor and the high pressure compressor of a gas turbine engine, the blow-off members opening as required, to allow the discharge of air into the secondary air flow path in order to avoid the problem of surging.
These blow-off members comprise a number of flaps which are distributed around the wall of the air flow path and are controlled synchronously. The control mechanism must be able to cause rapid opening and closure of the flaps and to maintain them in the closed position with no leakage of air. Accordingly, the control mechanism is relatively complicated.
As a result of the cumulative effect of play between the various components of the mechanism, the flaps that are furthest away from the actuator which controls their opening and closing are inadequately clamped against their seat and have a tendency to open slightly under the pressure of the air coming from the low pressure compressor. The leakage flow thus caused interferes with the operation of the high pressure compressor. In addition, the flaps have a tendency to flutter, which generates vibrations and, in the long term, causes their deterioration.
FR Patent 2 260 697 discloses a combined pressure boosting and relief mechanism comprising an assembly of booster valves formed by two panels, one for the primary flow and the other for the secondary flow, which are pivoted by a rack and pinion mechanism so that they open simultaneously in opposite directions into their respective flow paths to carry out a pressure boosting function. Each panel comprises a central flap, the two flaps opening symmetrically towards each other away from their respective flow paths to perform a relief function.
In this case also, play in the assembly does not ensure the proper closure of the flaps which effect the pressure relief function and they are therefore liable to open slightly and to flutter. In addition, the pressure in the secondary flow path is applied to the corresponding flaps and tends to open them slightly. Thus, the force applied to the control mechanism must be all the greater.